Polyolefin production with a high performance support for a metallocene catalyst system

ABSTRACT

The invention is directed to a metallocene catalyst system and a process for preparing the system. The metallocene catalyst system comprises a support and metallocene bound substantially throughout the support. The selection of certain supports facilitates the production of metallocene catalyst systems having increased catalytic activity than previously recognized.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention is directed, in general, to a metallocenecatalyst system for the production of polyolefins and more specifically,to a metallocene catalyst system that includes the selection of silicasupports within the catalyst system that provide increased catalyticactivity.

BACKGROUND OF THE INVENTION

[0002] Metallocenes are of increasing importance as a commercial olefinpolymerization catalyst. Typically, a metallocene catalytic system (MCS)is used in the polymerization of olefins. The MCS may comprise ametallocene and an activator on a support, for example, an inorganicsupport. Such activators are well known and typically include analuminum alkyl or aluminoxanes, such as methylaluminoxane (MAO). To forma conventional MCS, the metallocene and the optional alumoxane activatormay be reacted in the presence of the support to provide a supportedmetallocene-alumoxane reaction product. For example, a silica gelsupport may be coated with an alumoxane, such as methylalumoxane (MAO).A metallocene may be complexed with the alumoxane bound to the supportto form a MCS that can then be used in an olefin polymerization process.A trialkylaluminum or organoaluminum activator or scavenger maybeemployed during the polymerization process to increase catalyticactivity.

[0003] However, for such MCSs to provide an economically viablealternative to conventional catalysts, a number of limitations must beovercome. For example, the MCS must be capable of producing polymers ofthe desired stereospecificity and morphology. For example, stereoregularpolymers produced from such MCSs should have a certain desiredtacticity. Isotactic polypropylene (iPP) or syndiotactic polypropylene(sPP), for example, can be described as having the methyl groupsattached to the tertiary carbon atoms of successive monomeric unitsoriented on the same side, or alternating sides for sPP, of ahypothetical plane through the main chain of the polymer.

[0004] Desirable morphologic properties may include polymers comprisinguniform compact generally spherical particles, having a particularparticle size distribution, or a certain bulk density, and low contentof fine particles. The generation of undesirable fine particles (i.e.,particle diameter less than about 106 microns) can cause plant processdifficulties, such as plugging filters, and affect the accuracy of levelgauge readings. Alternatively, large particles (i.e., having a low bulkdensity) are also undesirable because they require more power tocirculate though loop reactors, leading to high power consumption andlower production rates.

[0005] Additionally, MCSs should ideally have high catalytic activity.One limiting factor in the production of MCSs with high activity isthought to be the low amount of activator or metallocene loaded onto tothe support. Another factor limiting catalytic activity is thought to bethe low amount of activated metallocene loaded onto the support.Moreover, as the costs for metallocene or activator can be substantial,their efficient use is important to controlling the total cost ofproducing a MCS.

[0006] Accordingly, what is needed in the art is a MCS that providesimproved activity, and yet still having acceptable morphologicalproperties, while overcoming the above-mentioned problems.

SUMMARY OF THE INVENTION

[0007] To address the above-discussed deficiencies, the presentinvention provides, in one embodiment, a metallocene catalyst system(MCS) that includes a support and a metallocene bound substantiallythroughout the support. On exposure to a reaction environment comprisingabout 300 g to about 400 g propylene per liter of reactor volume, about23 ppm by weight of said MCS, about 37 ppm by weight H₂, and about 46ppm by weight triethylaluminum in a 4 liter reactor at about 67° C. andabout one hour reaction time, the MCS has a catalytic activity of atleast about 10,400 g of polypropylene/g of MCS/hr.

[0008] Another embodiment is a MCS comprising a catalyst support systemincluding a support having an average pore diameter of greater thanabout 140 Angstroms and a metallocene bound substantially throughout thesupport. The MCS has a catalytic activity for a metallocene loading ofabout 2 wt % that is at least about 20 percent higher than saidcatalytic activity for said metallocene loading of about 1 wt %.

[0009] Another embodiment includes a process for the preparation of aMCS. The process includes providing a support having a surface definingpores and attaching a metallocene substantially throughout the supportto form a MCS. The MCS has a catalytic activity for a metalloceneloading of about 2 wt % that is at least about 20 percent higher thanthe catalytic activity for the metallocene loading of about 1 wt %.

[0010] In yet another embodiment, the present invention provides aprocess for producing a polyolefin. The process comprises preparing ametallocene catalyst system (MCS) having a catalytic activity for ametallocene loading of about 2 wt % that is at least about 20 percenthigher than the catalytic activity for the metallocene loading of about1 wt %. The process further includes introducing the MCS into apolymerization reaction chamber and contacting at least one olefinmonomer with the MCS in the reaction chamber.

[0011] Still another embodiment comprises a polyolefin produced byintroducing a metallocene catalyst system (MCS) into a polymerizationreaction chamber and contacting at least one olefin monomer with the MCSin the reaction chamber. The MCS has a catalytic activity for ametallocene loading of about 2 wt % that is at least about 20 percenthigher than the catalytic activity for the metallocene loading of about1 wt %.

[0012] The foregoing has outlined preferred and alternative features ofthe present invention so that those skilled in the art may betterunderstand the detailed description of the invention that follows.Additional features of the invention will be described hereinafter thatform the subject of the claims of the invention. Those skilled in theart should appreciate that they can readily use the disclosed conceptionand specific embodiment as a basis for designing or modifying otherstructures for carrying out the same purposes of the present invention.Those skilled in the art should also realize that such equivalentconstructions do not depart from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a more complete understanding of the invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawing, in which:

[0014]FIG. 1 illustrates a cross section through a portion of a MCS ofthe present invention;

[0015]FIG. 2 illustrates BJH-DFT analysis results of pore volumedistribution with respect to pore diameter for different silicas;

[0016]FIG. 3 illustrates BJH-DFT analysis results of surface areadistribution with respect to pore diameter for different silicas;

[0017]FIG. 4 illustrates a particle size distribution analysis of theMAO-modified silica supports; and

[0018]FIG. 5 illustrates a particle size distribution of polymerproduced using different silica supported MCS.

DETAILED DESCRIPTION

[0019] As further described below, the present invention discloses ametallocene catalyst system (MCS), a process for preparing the MCS, aprocess for preparing a polyolefin using the MCS, and the polyolefinproduced by that process, improving on that disclosed in U.S. Pat. Nos.6,143,683, 6,211,109, 6,225,251 and 6,239,058 to Shamshoum et al., andU.S. patent application Ser. Nos. 09/782,752 and 09/782,753 to Gauthieret al., all of which are incorporated herein by reference.

[0020] While not limiting its scope, the present invention is founded onthe theory that the final catalytic activity and performance of a MCSdepends on the support material used in the MCS. In particular, it hasbeen discovered that the catalyst polymerization activity of the MCS isstrongly dependent on the pore volume and surface area of the support.In particular, the selection of supports having optimal pore volume andsurface area distributions with respect to pore diameter cansubstantially improve the activity of the MCS.

[0021] In certain preferred embodiments, the pore volume and surfacearea distributions, as a function of pore diameter, are coincident witheach other. The terms pore volume and surface area distribution as usedherein refer, respectively, to the pore volume and surface area measuredfor the entire range of pore diameters present in a support. Theseparameters may be expressed as a total pore volume or total surfacearea, respectively, for example, as measured by conventional gasabsorption/desorption techniques and using the Brunauer, Emmett andTeller model (BET).

[0022] More usefully, however, the distributions of pore volumes andsurface areas over the range of pore diameters present in the supportmaterial, may be measured using conventional methods, such as theBarrett-Joyner-Halenda (BJH) method, and the Oliver-Conklin DensityFunction Theory (DFT). It is believed that supports, such as silicas,having different pore volume and surface area distribution, may alsohave different metallocene and activator supporting mechanisms andpolymerization behavior. Knowledge about the pore volume and surfacearea distribution for different silicas thus allows for the selection ofan optimal support for producing a MCS.

[0023] While not limiting the scope of the present invention by theory,it is believed that MCS activity is facilitated through the selection ofsupports of sufficiently large pore diameter to allow the metallocene topenetrate and interact with substantially all of the inner surface ofthe support. At the same time, the pore volume must not be too large soas to decrease the surface area available foractivator-metallocene-support interactions, or to create too fragile aMCS, such that it does not remain intact during the process forformation of the MCS or during the MCS's transport to a reactor.

[0024] In one embodiment, the present invention is directed to a MCScomprising a support and a metallocene bound substantially throughoutthe support wherein on exposure to a particular reaction environment theMCS has a catalytic activity of at least about 10,400 g ofpolypropylene/g of MCS/hr. The reaction environment may comprise about300 g to about 400 g propylene per Liter of reactor volume, about 23 ppmby weight of the MCS, about 37 ppm by weight H₂, and about 46 ppmtriethylaluminum in a 4 liter reactor at about 67° C. and about one hourreaction time. In one preferred embodiment, the metallocene, forexample, comprises rac dimethylsilanediyl bis(2-methyl-4-phenyl indenyl)zirconium dichloride.

[0025] For all catalytic reactions described herein, the use of polymergrade olefin monomers are preferred. Methods of preparing such monomers,and the purity of such monomers are well known to those of ordinaryskill in the art. In certain embodiments, the monomer is furtherpurified. For example, when the monomer is propylene, polymer gradepropylene having a minimum purity of 99.5 wt % was used after furtherpurification. Specifically, the polymer grade propylene was furtherpurified to remove known catalytic poisons, by sequential passagethrough columns containing: (1) a Nickel catalyst supported on Aluminafor carbonyl sulfide (COS) removal; (2) copper on alumina for O₂removal, (using e.g., BASF R3-11, BASF Corp., Mount Olive, N.J.); (3)molecular sieves for H₂O removal (using e.g., 3A, 4A, 5A or 13X orsimilar molecular sieves). Columns were activated using means well knownto those skilled in the art. Such treatments are expected to reduce COSlevels to less than about 20 ppb, and more preferably less than about 5ppb; reduce O₂ levels to less than about 5 ppm, and more preferably lessthan about 2 ppm; and reduce H₂O levels to less than 5 ppm, and morepreferably less than about 2 ppm.

[0026] In other preferred embodiments, the MCS has an activity of atleast about 11,900, and even more preferably at least about 12,100 ofpolypropylene/g of MCS/hr (g/g/hr), when the metallocene loading ontothe support is about 1 wt % (weight of metallocene per unit weight ofsupport). In other preferred embodiments, the MCS has an activity of atleast about 11,800, and more preferably at least about 14,040, and stillmore preferably at least about 19,000, and even more preferably at leastabout 23,000 polypropylene/g of MCS/hr, when the metallocene loading isabout 2%.

[0027] The term metallocene loading as used herein refers to the weightpercent of metallocene presented to the support during the preparationof the MCS, and resulting in metallocene bound substantially throughoutthe support. As further disclosed below, in certain preferredembodiments, the support comprises silica and an activator comprising analumoxane, for example, MAO, bound substantially throughout the silicasupport and the metallocene bound to the silica support via theactivator.

[0028] One skilled in the art would understand that in testing catalyticactivity, the amounts of the components in the reaction environment maybe varied, so as to provide about 30 to 50% conversion of monomer topolymer. Moreover, one skilled in the art would understand that thedesired reaction environment for testing the optimal catalytic activityof different metallocenes may differ from that described above. Thepolymerization reaction mixture may comprise, for example, differentproportions of propylene, MCS, hydrogen and TEAl. For example, theamount of MCS may range from about 10 ppm to about 150 ppm, by weight ofthe support, and more preferably from 10 ppm to and 100 pmm, withdecreased amounts used for higher activity MCSs. The amount of H₂ may bevaried to provide a polymer having a melt flow between about 2 and about60 g/10 min, and preferably about 10 g/10 min. H₂ may preferably be atleast about 5 ppm, and more preferably range between about 28 ppm toabout 37 ppm. The amount of TEAl used, typically ranging from about 46ppm to about 56 ppm, should be sufficient to scavenge inactivators ofMCS and provided a polymer having the desired melt flow. Moreover,cocatalysts other than TEAl, such as triisobutylaluminum(TiBAL), may beused.

[0029] A second aspect of the present invention is directed to a MCScomprising a catalyst support system including a support material havingan average pore diameter of a certain size. The MCS may comprise acatalyst support system including a support having an average porediameter of greater than about 140 Angstroms and a metallocene boundsubstantially throughout the support. The MCS has a catalytic activityfor a metallocene loading of about 2 wt % that is at least about 20percent higher than the catalytic activity for the metallocene loadingof about 1 wt %. More preferably, with 2 wt % of metallocene loading,the catalytic activity is at least about 55% higher, and more preferablyabout 85% higher, as compared to 1 wt % loading. In certain preferredembodiments, for example, the MCS has a catalytic activity of at leastabout 11,800 g/g/hr in a one hour reaction time under the reactionenvironment previously described herein.

[0030] Illustrated in FIG. 1 is a cross section through a portion of aMCS 100 of the present invention having an idealized, spherical pore110. In certain embodiments, the MCS 100 comprises a catalyst supportsystem 100, including a silica support 105 having pores 110 with adiameter D_(pore). In certain embodiments, D_(pore) may be greater thanabout 140 Angstroms, depending on the size of the metallocene andactivator bound to the support, as further discussed below. In certainpreferred embodiments D_(pore) may range from about 150 Angstroms toabout 450 Angstroms, and more preferably about 300 to about 310Angstroms.

[0031] In yet other embodiments, the MCS may further include an optionalactivator 115, such as an aluminoxane, having a diameter D_(act), andbound to the support 105. In such embodiments, the D_(act) may rangefrom about 1.0 nm to about 5.0 nm, and more preferably the D_(act) has avalue of about 1.5 nm. A metallocene 120 having a diameter D_(Me), maybe bound to the activator 115 within the pore 110. D_(Me) may range fromabout 0.5 nm to about 3.0 nm, and in certain preferred embodimentsD_(Me) may equal about 1.3 nm. Ideally, after the metallocene complexeswith the support, either directly or through an optional activator 115,there remains an open space within the pore 110 defined by a criticalpore diameter (CPD).

[0032] The D_(pore) is preferably sufficiently large to allow theoptional activator 115 to diffuse into and interact with substantiallythe entire surface area (i.e., both the exterior and interior) of thesupport 105 and attach thereto. Additionally, the CPD is sufficientlylarge to allow the metallocene 120 to diffuse throughout and interactwith the support 105 and attach thereto, or with the activator 115 boundto the support 105.

[0033] Any metallocene may be used in the practice of the invention. Asused herein unless otherwise indicated, “metallocene” includes a singlemetallocene composition or two or more metallocene compositions.Metallocenes are typically bulky ligand transition metal compoundsgenerally represented by the formula:

[L]_(m)M[A]_(n)   (1)

[0034] where L is a bulky ligand, A is a leaving group, M is atransition metal and m and n are such that the total ligand valencycorresponds to the transition metal valency.

[0035] The ligands L and A may be bridged to each other, and if twoligands L or A are present, they may be bridged. The metallocenecompound may be full-sandwich compounds having two or more ligands Lwhich, for example, may be cyclopentadienyl ligands (Cp) orcyclopentadiene derived ligands or half-sandwich compounds having oneligand L, which is a cyclopentadienyl ligand or cyclopentadienyl derivedligand. Other examples of ligands include fluorenyl (Flu), indenyl(Ind), azulenyl or benzylindenyl groups and their substitutedderivatives.

[0036] The transition metal atom may be a Group 4, 5, or 6 transitionmetal and/or a metal from the lanthanide and actinide series. Zirconium,titanium, and hafnium are desirable. Other ligands may be bonded to thetransition metal, such as a leaving group, such as, but not limited to,halogens, hydrocarbyl, hydrogen or any other univalent anionic ligand. Abridged metallocene may, for example, be described by the generalformula:

RCp(R′)Cp′(R″)MeQn   (2)

[0037] Me denotes a transition metal element and Cp and Cp′ each denotea cyclopentadienyl group, each being the same or different and which canbe either substituted with R′ and R″ groups having from 1 to 20 carbons,respectively, or unsubstituted, the Q groups may be independentlyselected from an alkyl or other hydrocarbyl or a halogen group, n is anumber and may be within the range of 1-3 and R is a structural bridgeextending between the cyclopentadienyl rings and comprising ahydrocarbyl radical.

[0038] Preferred metallocene-containing catalyst systems that produceisotactic polyolefins are disclosed in U.S. Pat. Nos. 4,794,096 and4,975,403 which are incorporated by reference herein. These patentsdisclose chiral, stereorigid metallocenes that polymerize olefins toform isotactic polymers and are especially useful in the polymerizationof highly isotactic polypropylene.

[0039] Other suitable metallocenes are disclosed in, for example, U.S.Pat. Nos. 4,530,914; 4,542,199; 4,769,910; 4,808,561; 4,871,705;4,933,403; 4,937,299; 5,017,714; 5,026,798; 5,057,475; 5,120,867;5,132,381; 5,155,180; 5,198,401; 5,278,119; 5,304,614; 5,324,800;5,350,723; 5,391,790; 5,436,305; 5,510,502; 5,145,819; 5,243,001;5,239,022; 5,329,033; 5,296,434; 5,276,208; 5,672,668; 5,304,614,5,374,752; 5,510,502; 4,931,417; 5,532,396; 5,543,373; 6,100,214;6,228,795; 6,124,230; 6,114,479; 6,117,955; 6,087,291; 6,140,432;6,245,706; 6,194,341; 6,399,723; 6,380,334; 6,380,331; 6,380,330;6,380,124; 6,380,123; 6,380,122; 6,380,121; 6,380,120; 6,376,627;6,376,413; 6,376,412; 6,376,411; 6,376,410; 6,376,409; 6,376,408;6,376,407; 6,087,29; 5,635,437; 5,554,704; 6,218,558; 6,252,097;6,255,515 and EP 549 900; EP 576 970; EP 611 773, and WO 97/32906; WO98/014585; WO 98/22486; and WO 00/12565, each of which is fullyincorporated by reference herein in its entirety.

[0040] In certain preferred embodiments, the metallocene is one or moreof an isospecific stereo rigid metallocene characterized by the formula:

R²bis(C₅(R¹)_(n))MeQ_(p)   (3)

[0041] wherein each (C₅(R¹)_(n)) is a substituted cyclopentadienyl ringand n may range from 1 to 20 so long as the number of sites availablefor substitution are not exceeded. Each R¹ is the same or different andis a hydrogen or hydrocarbyl radical having 1-20 carbon atoms. R² is astructural bridge between the two (C₅(R¹)_(n)) rings impartingstereorigidity to the metallocene, and imparting a chiral environment toa metal, Me. R² is selected from the group consisting of an aykyleneradical having 1-4 carbon atoms, a silicon hydrocarbyl radical, agermanium hydrocarbyl radical, a phosphorus hydrocarbyl radical, anitrogen hydrocarbyl radical, a boron hydrocarbyl radical, and analuminum hydrocarbyl radical. The Me is a group 4, 5, or 6 metal asdesignated in the Periodic Table of Elements. Each Q may beindependently selected from a hydrocarbyl radical having 1-20 carbonatoms or is a halogen; and 0≦p≦3.

[0042] In certain advantageous embodiments, the structural bridge R²,among other things, holds the two (C₅(R¹)_(n)) rings in a desired chiralorientation to facilitate the production of an isotactic polymer. Forexample, when the two (C₅(R¹)_(n)) rings are identical, a racemicorientation is preferred over a meso orientation. In cases where the two(C₅(R¹)_(n)) rings are nonidentical, then the structural bridge R² holdsthe ring's orientation to generate the appropriate chirality, forexample, to produce isotactic polymer.

[0043] In other advantageous embodiments, the (C₅(R¹)_(n)) groups areindenyl groups which are substituted or unsubstituted. In still otherpreferred embodiments, the metallocene may be rac dimethylsilanediylbis(2-methyl-4-phenyl indenyl) zirconium dichloride. In yet otheradvantageous embodiments metallocene may be selected from the groupconsisting of rac dimethylsilanediyl bis(2-methyl indenyl) zirconiumdichloride, rac dimethylsilanediyl bis(2-methyl-4,5-benzoindenyl)zirconium dichloride and rac dimethylsilanediylbis(2-methyl-4-(1-naphthyl) indenyl) zirconium dichloride.

[0044] The term activator, as used herein, refers to any compound orcomponent, or combination of compounds or components, capable ofenhancing the ability of one or more metallocenes to polymerize olefinsto polyolefins. In particular embodiments, the activator is any compoundcapable of generating a catalytically activated cationic center. Oneparticularly useful class of activators are based on organoaluminumcompounds, which may take the form of an alumoxane, such as MAO or amodified alkylaluminoxane compound. Alumoxane (also referred to asaluminoxane) is an oligomeric or polymeric aluminum oxy compoundcontaining chains of alternating aluminum and oxygen atoms, whereby thealuminum carries a substituent, preferably an alkyl group. The exactstructure of aluminoxane is not known, but is generally believed to berepresented by a caged or clustered compound, comprised of componentshaving the following general formula: —(Al(R)—O—)_(−m), for cyclicalumoxane components, and R₂Al—O—(Al(R)—O)_(m)—AlR₂ for linear alumoxanecomponents, wherein R independently in each occurrence is a C₁-C₈hydrocarbyl, preferably alkyl, more preferably C₁, or halide, and m ispreferably an integer ranging from about 1 to about 40, and morepreferably about 4 to about 30, and even more preferably about 10 toabout 20.

[0045] Alumoxanes are typically the reaction products of water and analuminum alkyl, which in addition to an alkyl group may contain halideor alkoxide groups. Reacting several different aluminum alkyl compounds,for example, trimethylaluminum (TMA) and tri-isobutyl aluminum, with acorrect stoichiometry of water yields so-called modified or mixedalumoxane activators. Other non-hydrolytic routes for the production ofactivators are well known to those of ordinary skill in the art.Preferred alumoxanes are MAO and MAO modified with minor amounts ofother higher alkyl groups such as isobutyl. Alumoxanes generally containminor to substantial amounts of starting aluminum alkyl compound(s).Other activators include trialkylaluminum, such as TEAl ortriisobutylaluminum (TIBAL) or mixtures thereof. Alumoxane solutions,particularly MAO solutions, may be obtained from commercial vendors assolutions having various concentrations (e.g., Albermarle Corp., BatonRouge, La.; Akzo Nobel Catalysts Ltd., Houston, Tex.; Crompton Corp.,Greenwich, Conn.).

[0046] There are a variety of methods for preparing alumoxane,non-limiting examples of which are described in U.S. Pat. Nos.4,665,208, 4,952,540, 5,091,352, 5,206,199, 5,204,419, 4,874,734,4,924,018, 4,908,463, 4,968,827, 5,308,815, 5,329,032, 5,248,801,5,235,081, 5,103,031 and EP-A-0 561 476, EP 0 279 586, EP-A-0 594 218and WO 94/10180, each fully incorporated herein by reference. As usedherein, unless otherwise stated, “solution” refers to any mixtureincluding suspensions.

[0047] Ionizing activators may also be used to activate metallocenes.These activators are neutral or ionic, or organoboron compounds, such astri(n-butyl)ammonium tetrakis (pentaflurophenyl)borate, which ionize theneutral metallocene compound. Such ionizing compounds may contain anactive proton, or some other cation associated with, but not coordinatedor only loosely coordinated to, the remaining ion of the ionizingcompound. Combinations of activators may also be used, for example,alumoxane and ionizing activators in combinations, see e.g., WO94/07928, incorporated herein by reference.

[0048] Descriptions of ionic catalysts for coordination polymerizationcomprised of metallocene cations activated by non-coordinating anionsappear in EP-A-0 277 003, EP-A-0 277 004 and U.S. Pat. No. 5,198,401 andWO-A-92/00333 (incorporated herein by reference). These teach a methodof preparation wherein metallocenes, such as bisCp and monoCp, areprotonated by an anion precursor such that an alkyl/hydride group isabstracted from a transition metal to make it both cationic andcharge-balanced by the non-coordinating anion. Suitable ionic saltsinclude tetrakis-substituted borate or aluminum salts having fluorinatedaryl-constituents such as phenyl, biphenyl and naphthyl.

[0049] The term noncoordinating anion (NCA) as used herein refers to ananion that either does not coordinate to the cation or that is onlyweakly coordinated to the cation, thereby remaining sufficiently labileto be displaced by a neutral Lewis base, and allows for monomercoordination and insertion. “Compatible” noncoordinating anions arethose which are not degraded to neutrality when the initially formedcomplex decomposes. Further, the anion will not transfer an anionicsubstituent or fragment to the cation so as to cause it to form aneutral four coordinate metallocene compound and a neutral by-productfrom the anion.

[0050] The use of ionizing ionic compounds not containing an activeproton but capable of producing both the active metallocene cation and anoncoordinating anion are also known. See e.g., EP-A-0 426 637 andEP-A-0 573 403, both incorporated herein by reference. An additionalmethod of making the ionic catalysts uses ionizing anion precursorswhich are initially neutral Lewis acids but form the cation and anionupon ionizing reaction with the metallocene compounds, for example, theuse of tris(pentafluorophenyl) borane, see e.g., EP-A-0 520 732,incorporated herein by reference. Ionic catalysts for additionpolymerization can also be prepared by oxidation of the metal centers oftransition metal compounds by anion precursors containing metallicoxidizing groups along with the anion groups, see e.g., EP-A-0 495 375,incorporated herein by reference.

[0051] Where the metal ligands include halogen moieties, for example,bis-cyclopentadienyl zirconium dichloride, that are not capable ofionizing abstraction under standard conditions, they can be convertedvia known alkylation reactions with organometallic compounds, such aslithium or aluminum hydrides or alkyls, alkylalumoxanes, Grignardreagents, and other reaction well know to those skilled in the art. SeeEP-A-O 500 944 and EP-Al-0 570 982, both incorporated herein byreference, for in situ processes describing the reaction of alkylaluminum compounds with dihalo-substituted metallocene compounds priorto or with the addition of activating anionic compounds.

[0052] Methods for supporting ionic catalysts comprising metallocenecations and NCA are described in U.S. Pat. Nos. 5,643,847, 6,143,686 and6,228,795, all incorporated herein by reference. When using the supportcomposition, these NCA support methods generally comprise using neutralanion precursors that are sufficiently strong Lewis acids to react withthe hydroxyl reactive functionalities present on the silica surface suchthat the Lewis acid becomes covalently bound.

[0053] Additionally, when the activator for the metallocene supportedcatalyst composition is a NCA, the NCA is preferably first added to thesupport composition followed by the addition of the metallocene. Whenthe activator is MAO, the MAO is preferably contacted with the support,and then the metallocene is contacted to the supported MAO.Alternatively, the MAO and metallocene may be dissolved together insolution and then the support is contacted with the MAO/metallocenesolution. Other methods and order of addition will be apparent to thoseof ordinary skill in the art, and as further described below.

[0054] Various types of metallocenes are known in the art which may besupported. The supports may include talc, inorganic oxides, clayminerals, ion-exchanged layered compounds, diatomaceous earth,silicates, zeolites or a resinous support material such as a polyolefinor mixtures therefrom. Specific inorganic oxides include clay, silicaand alumina, used alone or in combination with other inorganic oxidessuch as magnesia, titania, zirconia and the like. Non-metallocenetransition metal compounds, such as titanium tetrachloride, may also beincorporated into the supported catalyst component.

[0055] In certain embodiments when the support comprises an inorganicoxide, the support may be substantially granular. In certain preferredembodiments, the inorganic oxide support is substantially spheroidal. Insuch embodiments, the support may have an average particle size diameterranging from about 1 to about 100 microns, and more preferably about 10to about 60 microns.

[0056] In certain preferred embodiments, the support has an averageparticle size ranging from about 10 to about 33 microns, and morepreferably from about 10 to about 20 microns. Such preferred embodimentsmay be conducive to the production of smaller sized polymer fluffshaving average diameters of less than about 600 microns yet still havinga desirably high bulk density, for example, at least about 0.40 g/cc,and more preferably at least about 0.44 g/cc.

[0057] In certain alternative preferred embodiments, the support has anaverage particle size ranging from about 20 to about 80 microns, andmore preferably from about 25 to about 60 microns. For a MCS of a givenactivity, such preferred embodiments may be conducive to the productionof larger sized polymer fluffs having average diameters of greater thanabout 600 microns, and yet still having the above-mentioned desirablyhigh bulk density.

[0058] A third aspect of the present invention is directed to a processfor the preparation of a MCS. The process comprises providing a supporthaving a surface defining pores. The process further comprises attachinga metallocene substantially throughout the support to form a MCS havinga catalytic activity for a metallocene loading of about 2 wt % that isat least about 20 percent higher than the catalytic activity for themetallocene loading of about 1 wt %. In certain preferred embodiments,for example, the process results in a MCS having a catalytic activity ofat least about 11,800 g/g/hr in a one hour reaction time under thereaction environment previously described herein. In other preferredembodiments, the support comprises granular or substantially spheroidalmaterials, such as silica. In yet other preferred embodiments, anactivator, such as MAO, may be conventionally attached to the poressubstantially throughout the support material to form a catalyst supportto which the metallocene attaches.

[0059] In other embodiments, the pores in the support provides a peakpore volume of greater than about 0.115 mL/g at a pore diameter ofgreater than about 240 Angstroms. Preferably, however, at the peak porevolume, the pore diameter ranges between about 250 Angstroms and about350 Angstroms. More preferably, the spheroidal supports have a peak porevolume of greater than about 0.125 mL/g at a pore diameter between about290 Angstroms and about 320 Angstroms. Even more preferably, the peakpore volume is greater than about 0.13 mL/g at a pore diameter of about300 to about 310 Angstroms. In other advantageous embodiments, the porevolume is distributed over a narrow range. For example, the support'spore diameter may be between about 230 Angstroms and about 410Angstroms, at one-half of the peak pore volume.

[0060] In still other embodiments, the pores in the support provide apeak surface area of at least about 14.3 m²/g at a pore diameter betweenabout 250 Angstroms and about 330 Angstroms, and preferably, betweenabout 260 Angstroms and about 320 Angstroms. Even more preferably, thesupport may have a peak surface area of at least about 17 m²/g in theabove-cited range of pore diameters.

[0061] Although pore volume and surface area distributions are thepreferred measures for the purpose of selecting and providing optimalsupports, alternative selection criteria may be used. For example, incertain embodiments, the support further may have a total pore volume ofgreater than about 1.68 mL/g and an average pore diameter between about242 Angstroms and about 253 Angstroms. In an alternative embodiment,however, the total pore volume may be less than about 1.79 mL/g for asupport having the above-cited range of average pore diameters. In stillother embodiments, the total surface area is greater than about 272 m²/gfor a support having the above-cited range of average pore diameters.

[0062] A fourth aspect of the present invention is directed to a processfor the polymerization of polyolefin. The process includes preparing ametallocene catalyst system (MCS) having a catalytic activity for ametallocene loading of about 2 wt % that is at least about 20 percenthigher than the catalytic activity for the metallocene loading of about1 wt %. Preparing the MCS includes the selection of supports based onconsiderations of the critical pore diameter, and the pore volume andsurface area distribution of candidate supports as described elsewhereherein. The process also includes introducing the MCS into aconventional polymerization reaction chamber. The process furtherincludes contacting at least one olefinic monomer with the MCS in thereaction chamber under conventional conditions.

[0063] In certain preferred embodiments, for example, the processresults in a MCS having a catalytic activity of at least about 11,800g/g/hr in a one hour reaction time under the reaction environmentpreviously described herein. In other preferred embodiments, any alphaolefins, comprising ethylenically unsaturated hydrocarbons havingbetween 2 and 20 Carbon atoms, may be used as the monomer. In yet otherpreferred embodiments, the process for polymerization may include, forexample, an olefinic monomer comprising propylene contacted with the MCSto produce a homopolymer. Preferred reaction conditions may include areaction temperature between about 50 to about 75° C., and preferably67° C., a reaction period between about 15 minutes and 120 minutes, andinclude hydrogen gas and TEAl in the reaction chamber, in amountdescribed elsewhere herein. Other embodiments may further comprise, forexample rac dimethylsilanediyl bis(2-methyl-4-phenyl indenyl) zirconiumdichloride, having up to about 2 wt % of the metallocene loaded onto thesupport, and an alumoxane activator comprising methylaluminoxane.

[0064] In yet other embodiments, the above-described process may be usedto produce a polyolefin comprising a copolymer under reaction conditionspreviously described herein. Any combination of alpha olefins,comprising ethylenically unsaturated hydrocarbons having between 2 and20 Carbon atoms, may be used as the monomer. For example, one preferredmonomer mixture comprises propylene and ethylene. Other preferredmonomer mixtures may include propylene, butene and ethylene, orpropylene and butene.

[0065] A fifth aspect of the present invention is directed to apolyolefin produced by any of the above-described processes. The processcomprises introducing a MCS into a polymerization reaction chamber. TheMCS has a catalytic activity for a metallocene loading of about 2 wt %that is at least about 20 percent higher than the catalytic activity forthe metallocene loading of about 1 wt %. The process further comprisescontacting at least one olefin monomer with the MCS in the reactionchamber.

[0066] In certain preferred embodiments, the polyolefin is produced by aMCS having a catalytic activity of at least about 11,800 g/g/hr in a onehour reaction time under the reaction environment previously describedherein. In other preferred embodiments, the polyolefins may be convertedto resins used in the manufacture a variety of end products such asfilms, fibers, injection molded articles and other materials well knownto one of ordinary skill in the art. In other advantageous embodiments,the metallocene may comprise rac dimethylsilanediylbis(2-methyl-4-phenyl indenyl) zirconium dichloride and an alumoxaneactivator comprises methylaluminoxane.

[0067] In yet other preferred embodiments, the polyolefin produced, forexample isotactic polypropylene, has an average particle size diameterof greater than about 200 microns. Certain preferred embodiments mayinclude polymer fluffs having a certain particle size. For example, theaverage polymer fluff diameter may be between about 400 microns andabout 2000 microns, and preferably between about 600 and about 1500microns. Such particle sizes may be more advantageously produced incertain plant-scale reactor facilities, such as loop type reactors, andpost-reactor processing facilities that are designed to handle suchsized polymer fluffs.

[0068] In yet other preferred embodiments, the production of differentsized polymer fluffs may be advantageous. For example, the averagepolymer fluff diameter may be between about 500 microns and about 1500microns, and more preferably between about 600 and about 1200 microns.Such particle sizes may be more advantageous in certain plant-scaleproduction facilities having reactors, such as Spheripol™ type reactors,and post-reactor processing, such as the devolitization and transport,designed to handle such sized polymer fluffs.

[0069] In still other embodiments, the polyolefin produced, for exampleisotactic polypropylene, may have a bulk density of at least about 0.37and more preferably at least about 0.40 g/cc, and even more preferablyat least about 0.44 g/cc.

[0070] Having described the present invention, it is believed that thesame will become even more apparent by reference to the followingexperiments. It will be appreciated that the experiments are presentedsolely for the purpose of illustration and should not be construed aslimiting the invention. For example, although the experiments describedbelow may be carried out in laboratory or pilot plant settings, oneskilled in the art could adjust specific numbers, dimensions andquantities up to appropriate values for a full scale plant.

[0071] Experiments

[0072] Four experiments were conducted to compare: (1) the porecharacteristics of several silica supports; (2) the loading of activatoronto the supports; (3) the catalytic activity of MCSs prepared using thesupports; and (4) the properties of polymers produced frompolymerization reactions catalyzed by the above-prepared MCSs.

[0073] Experiment 1

[0074] Six silica supports were selected for comparison: (1) productnumber Cariact P-10, from Fuji Silysia Chemical Company, Ltd. (Japan);(2) product number Sylopol 948 (“G-948”), (3) product number Sylopol952-1836 (“G-952”), and (4) product number XPO-2412, all from GraceDavison Chemicals (Columbia, Md.); (5) product number ES747JR, fromINEOS Silicas Ltd. (England); and (6) product number Sunsphere H202,from Asahi Glass Co. Ltd. (Japan). The average particle size of thesilicas was determined using a conventional Malvern sizer andmethodology in hexane or acetone. The analysis of the porecharacteristics (i.e., pore volume, surface area, pore diameter anddistributions) was conducted on an ASAP 2400 (Micromeritics InstrumentCorp., Norcross, Ga.), using nitrogen as the adsorbate for theconventional measurements of adsorption and desorption isotherms. Thedata was used for the calculation, using the BET model, of total surfacearea, total pore volume and average pore diameter. In addition, the datawere analyzed to determine, using the BJH method and DFT, the porevolume and surface area distributions.

[0075] TABLE 1 summarizes the total surface area, total pore volume andaverage pore diameter for the six silicas. Typical standard deviationsare ±5% for determination of surface area, pore volume and porediameter, and ±10% for the determination of particle size, using hexane.All six silicas had total surface areas of at least about 260 m²/g andhigh pore volume of at least about 1.4 mL/g. The average supportparticle size ranged from about 20 to about 33 microns, except for G-948at about 55 microns. TABLE 1 Surface Pore Avg. Area Volume Average PoreParticle Support (m²/g) (mL/g) Diameter (Å) Size (μm) P10 ˜270 ˜1.5 ˜222 ˜20 G-952 ˜278 ˜1.68 ˜242 ˜33 G-948 ˜272 ˜1.71 ˜253 ˜55 ES747JR˜263 ˜1.60 ˜244 ˜20 XPO-2412 ˜474 ˜1.53 ˜129 ˜21 H202 ˜678 ˜1.53 ˜90 ˜23

[0076] The pore volume and surface area distributions for the silicaswere also measured. The BJH method was used for calculating thesedistributions, based on a model of the adsorbent (i.e., the silicacarrier) as a collection of cylindrical pores. The calculation accountsfor capillary condensation in the pores using the classical Kelvinequation (free energy of surface tension), which in turn assumes ahemispherical liquid-vapor meniscus and a well-defined surface tension.The calculation also incorporates thinning of the adsorbed layer throughthe use of a reference isotherm, so that the Kelvin equation is onlyapplied to the “core” fluid.

[0077] In addition, the DFT was used to make distribution calculationsusing conventional mathematical, statistical, and numerical techniquesfor interpreting data from the ASAP 2400 instruments. The DFT offers aunified approach to analyzing the entire adsorption isotherm from about4 to about 1000 Å in diameter. All pores, from the smallest to thelargest, are reported using a single data reduction technique, termed asthe BJH-DFT reduction, thereby providing a broad picture of adsorptionactivity.

[0078]FIG. 2 illustrates BJH-DFT analysis results of pore volumedistribution with respect to pore diameter for the different silicas.FIG. 2 reveals that, even though XPO-2412 and H202 have high total porevolumes (TABLE 1), most of the pores had diameters of less than about150 Å. As such, these silicas are unlikely to provide substantialnumbers of pores having a CPD in a range suitable for most metallocenes.In addition, it is thought that silicas having a substantial number ofpores with a pore diameter larger than about 400 Å, may not be suitablebecause some of the pore space may be incompletely filled, thusinefficiently used as a support. Silicas, such as G-948, G-952, ES747JRand P10, have the bulk of their pore volumes distributed between 150 and400 Å. Among these four silicas, G-948 had the highest amount of porevolume distributed between 150 and 400 Å, and P10 the lowest.

[0079]FIG. 3 illustrates BJH-DFT analysis results of surface areadistribution with respect to pore diameter for the different silicas.Again, although H202 and XPO-2412 have high total surface areas (TABLE1), most of the surface area, is allotted to small pores with diametersof less about 150 Å. For example, most of the surface area for H202 isaccounted by small pores, having diameters of less than about 40 Å.Taking the results from FIGS. 3 and 4 together, for XPO-2412 and H202,most of the pores with the small pore diameters account for the mainsurface area but little of the pore volume. For the G-948, G-952,ES747JR and P10 silicas, the main pore volume is distributed between 140and 400 Å. Moreover, comparison of FIGS. 3 and 4 reveal that both thepore volume and surface area have the same distribution trends versuspore diameter for these four silica carriers. Again, among these four,G-948 had the highest amount of surface area distributed between 150 and400 Å, and P10 the lowest.

[0080] Experiment 2

[0081] The loading of activator into the six silica supports was alsoexamined. The reaction between silicas and MAO (Albermarle Corp., BatonRouge, La.) was conducted substantially as described in U.S. patentapplication Ser. Nos. 09/782,752 and 09/782,753 to Gauthier et al,incorporated by reference. Briefly, unless otherwise indicated, all thesilica supports were dried at 150° C. for 12 hours under nitrogen flowof 6 mL/min. Two processes were used, as described in the above-citedapplications: room temperature grafting (Process 1) and grafting at 115°C. (Process 2). For Process 1, room temperature grafting in toluene wascarried out with the starting concentration ratio of MAO:silica equal toabout 0.70:1.00, except for XPO-2412 and H202, where the ratio was about1:1. Process 2, involved grafting at 115° C. in toluene for 4 hours,with the starting concentration ratio of MAO:silica equaled about1.0:1.0 MAO:silica for all silicas, except H202 whose ratio was 1.35:1.Following grafting, both Process 1 and 2 work-ups included filtrationand several toluene washes to remove excess Al species.

[0082] The extent of MAO grafting achieved for the six silicas wasassessed by measuring Maximium Grafting Yield (MGY), defined by theformula:

MGY=((W ₂ −W ₁)/W ₁)·100%   (3)

[0083] where W₂ is defined as the weight of the MAO-modified silicasupport, and W₁ is the weight of the support before grafting. Thestandard deviation in MGY values is estimated to be about ±0.2 wt %. Theresult of these measurements are shown in TABLE 2.

[0084] For all six silicas, Process 2 resulted in a higher loading ofMAO onto the silica support than Process 1. Using Process 1, P10 had thelowest MGY at room temperature, with G-948 and G-952 having about 20%greater yields. The MGY for ES747JR, G-948, and G-952, were all lessthan about 6.4% higher for Process 1 compared to Process 2. TABLE 2 MGY(wt %) Support Process 1 Process 2 P10 ˜44.0  ˜62.5  ES747JR ˜52.8 ˜57.2  G-948 ˜57.1  ˜61.1  G-952 ˜59.2  ˜65.6  XPO-2412 ˜72.5  ˜83.6 H202 ˜100.0 ˜135.0

[0085] A particle size distribution analysis of the MAO-modified silicasupports was performed using the above-mentioned Malvern Sizer. Theanalysis, illustrated in FIG. 4, reveals that all the MAO-modifiedsupports contain a small shoulder peak having an average particle sizeof less than about 20 μm, which has been tentatively assigned to MAOgels. FIG. 4 reveals that ES747JR had a relatively larger MAO gelcontent than the other five silicas.

[0086] Experiment 3

[0087] In another series of experiments, the catalytic activity of MCSsprepared using the above-described silica supports was measured. Anadditional support, product number MS-1733 from PQ Corp. (Valley Forge,Pa.), was also tested. The total surface area (˜311 m²/g), pore volume(˜1.79 mL/g) and average particle size (˜74 μm) of the MS-1733 supportwas determined using the same methodology as described above.

[0088] The metallocene, rac dimethylsilanediyl bis(2-methyl-4-phenylindenyl) zirconium dichloride, was loaded in the MAO-modified silicasthat were prepared similar to that described above for Experiment 2. Toprepare the MCS, about 2.5 g of MAO-modified silica was mixed with 25mLs of toluene at room temperature under nitrogen. The metallocene(about 25 mg; designated as 2% metallocene loading) in about 10 mL oftoluene was added to MAO-modified silica under stirring. The mixture wasallowed to react for about 2 hours at room temperature (about 22° C.).The MCS was then filtered and washed three times with toluene (3×10 mL)and three times with hexane (3×10 mL) under nitrogen at roomtemperature. After an optional drying step at room temperature undervacuum to a constant weight, the resulting MCS was diluted into about 25g of mineral oil and then isolated as a solid slurry. The process forpreparing the MCS with a lower amount of metallocene loading (designatedas 1% metallocene loading) was carried out similar to that describedabove except that a correspondingly lower ratio of metallocene toMAO-modified silica was used.

[0089] The catalytic activity (CA) of the MCS was measured using themethodology substantially similar to that described in U.S. patentapplication Ser. Nos. 09/782,752 and 09/782,753 to Gauthier et al.Specifically, polymerization was carried out in a conventional 2 or 4Liter reaction chamber, in the presence of about 28 ppm H₂ (2 L reactor)or 37 ppm (4L reactor), about 28 ppm (2 L reactor) or about 23 ppm (4 Lreactor) of MCS, about 56 ppm (2 L reactor) or about 46 ppm (4 Lreactor) of TEAL, at about 67° C. for about one hour using about 300 toabout 400 g propylene per liter of reactor volume. Catalytic activity isthus expressed as g of polypropylene produced per g of MCS per 1 hr(g/g/hr). For all experiments, polymer grade propylene (minimum purity99.5 wt %) was used after further purification steps, describedelsewhere herein, to reduce levels of COS, O₂, and H₂O.

[0090] The catalytic activity for MCSs prepared from the seven differentMAO-modified silica carriers prepared at room temperature (Process 1)and 1 wt % metallocene loading, and high temperature (Process 2) and 1or 2 wt % metallocene loading are illustrated in TABLE 3. TABLE 3Process 1 Process 2 Process 2 (1 wt % loading) (1 wt % loading) (2 wt %loading) MAO:Si MAO:Si MAO:Si Silica Support (wt:wt) CA (g/g/hr) (wt:wt)CA (g/g/hr) (wt:wt) CA (g/g/hr) P10 0.44:1 ˜3400 0.62:1 ˜10300 0.62:1˜11700  G-948 0.57:1 ˜5400 0.61:1 ˜12100 0.61:1 ˜18800  G-952 0.59:1˜6500 0.69:1 ˜11900 0.69:1 ˜22200  ES747JR 0.53:1 ˜4100 0.57:1 ˜8500 XPO-2412 0.72:1 ˜5500 0.84:1 ˜9700  H202  1.0:1 ˜6600  MS-1733 0.76:1˜23,500

[0091] For supports prepared with similar starting ratios of MAO tosilica (MAO:Si), the MCSs produced from either Process 1 or 2, havingG-948 and G-952 supports, had the highest catalytic activity. Asindicated in TABLE 3, similar MAO:Si ratios were used, except forXPO-2412 and H202, where higher ratios were used. Also, the MCSsproduced from Process 2 had higher activity than the MCSs produced fromProcess 1. It is thought that heating and refluxing facilitates thefixation of MAO on the silica, thus increasing the space available tocontribute to the CPD, as compared to MAO fixation done at roomtemperature. It is thought that the pore volume and pore areadistribution of preferred supports, such as G-948, G-952, and MS-1733allow greater amounts of metallocene to be bound and activated in theinterior pores in these supports, as compared to other non-preferredsupports, such as P10, thereby resulting in greater catalytic activity.

[0092] The beneficial effect of higher amounts of metallocene loading oncatalytic activity for certain MCSs having high surface area and porevolume supports is illustrated in TABLE 3. For example, for P10supported MCSs, the enhancement in catalytic activity per unit weight ofMCS was less than about 14% when the metallocene loading was increasedto about 2 wt %, compared to the catalytic activity obtained with about1 wt % metallocene loading. In contrast, the catalytic activity forG-948 supported MCS using a metallocene at 2.0 wt % loading was at leastabout 20% higher, and in some cases greater than about 55% or greaterthan about 85% higher, as compared to the catalytic activity at 1.0 wt %loading. In another experiment even higher activity, 22,600 g/g/hr, wasobtained when a G-952 supported MCS was loaded with 2.5 wt %metallocene.

[0093] Experiment 4

[0094] A fourth series of experiments were conducted to characterize thepolymers produced from polymerization reactions carried out underconditions similar to that described in Experiment 3. For all of theMCSs, an isotactic polypropylene was produced, having for example, ameso pentad content of at least about 95% and a regioregularity ofgreater than about 99.0%. Polymer melt flow (MF) was recorded on aTinius-Olsen Extrusion Plastometer at 230° C. with a 2.16 Kg mass.Polymer powder was stabilized with approximately 1 mg of2,6-ditert-butyl-4-methylphenol (BHT) to prevent degradation in the MFindexer. Bulk density (BD) measurements were conducted by weighing theunpacked contents of a 100 mL graduated cylinder containing the polymerpowder. The polymer fluff particle size distribution was measured usinga conventional sieve shaker.

[0095] TABLE 4 illustrates the melt flow and bulk density properties ofpolypropylene produced under the conditions used to produce the MCSdescribed in TABLE 3. The melt flow of the polymers, including polymerproduced using G-948 and G-952 supported MCS, was acceptable, having avalue of greater than about 0.1 g/10 min. The bulk densities of polymerproduced using Process 1 or 2 with G-948 and G-952 supported MCS werealso had acceptable values, greater than about 0.35 g/cc, similar tothat obtained for polymers produced using MCSs supported by the othersilicas. TABLE 4 Process 1 Process 2 Silica MF BD MF BD Support (g/10min) (g/cc) (g/10 min) (g/cc) P10 ˜5  ˜0.42 ˜2   ˜0.42 G-948 ˜9  ˜0.37˜1   ˜0.37 G-952 ˜3  ˜0.38 ˜0.8 ˜0.41 ES747JR ˜11 ˜0.36 ˜0.4 ˜0.40XPO-2412 ˜8  ˜0.38 ˜2   ˜0.40 H202 ˜3   ˜0.44

[0096] The particle size distribution of polymer produced using Process2 and six of the silica supported MCS is shown in FIG. 5. Of these,polymer produced using G-948 supported MCS had the largest particlesize. The polypropylene produced using G-948 and G-952 supported MCSboth had a median particle size (an accumulative wt % equal to about50%) of greater than about 600 microns.

[0097] Although the present invention has been described in detail,those skilled in the art should understand that they can make variouschanges, substitutions and alterations herein without departing from thescope of the invention.

What is claimed is:
 1. A metallocene catalyst system (MCS) comprising: asupport; and a metallocene bound substantially throughout said support,wherein on exposure to a reaction environment comprising about 300 g toabout 400 g propylene per Liter of reactor volume, about 23 ppm byweight of said MCS, about 37 ppm by weight H₂, and about 46 ppmtriethylaluminum in a 4 liter reactor at about 67° C. and about one hourreaction time, said MCS has a catalytic activity of at least about10,400 g of polypropylene/g of MCS/hr.
 2. The MCS as recited in claim 1wherein said metallocene comprises rac dimethylsilanediylbis(2-methyl-4-phenyl indenyl) zirconium dichloride and said propylenecomprises polymer grade propylene further purified to having COS levelsof less than about 20 ppb, O₂ levels of less than about 5 ppm and H₂Olevels of less than about 5 ppm.
 3. The MCS as recited in claim 1wherein said catalytic activity is obtained for a metallocene loading upto about 1 wt %.
 4. The MCS as recited in claim 3 wherein said catalyticactivity is at least about 11,800 g of said polypropylene/g of saidMCS/hr.
 5. The MCS as recited in claim 1 wherein said catalytic activityis at least about 14,040 g of said polypropylene/g of said MCS/hr. 6.The MCS as recited in claim 5 wherein said catalytic activity isobtained for a metallocene loading of up to about 2 wt %.
 7. The MCS asrecited in claim 1 wherein said catalytic activity obtained for ametallocene loading of about 2 wt % is at least about 20 percent higherthan said catalytic activity obtained for a metallocene loading of about1 wt %.
 8. A metallocene catalyst system (MCS) comprising: a catalystsupport system including a support having an average pore diameter ofgreater than about 140 Angstroms; and a metallocene bound substantiallythroughout said support, said MCS having a catalytic activity for ametallocene loading of about 2 wt % that is at least about 20 percenthigher than said catalytic activity for said metallocene loading ofabout 1 wt %.
 9. The MCS as recited in claim 8 wherein said average porediameter is between about 150 Angstroms and about 450 Angstroms.
 10. TheMCS as recited in claim 8 wherein said metallocene is one or more of anisospecific stereo rigid metallocene characterized by the formula: R²bis (C₅(R¹)_(n))MeQp wherein each (C₅(R¹)_(n)) is a substitutedcyclopentadienyl ring; n may range from 1 to 20 so long as the number ofsites available for substitution are not exceeded; each R¹ is the sameor different and is a hydrogen or hydrocarbyl radical having 1-20 carbonatoms; R² is a structural bridge between said two (C₅(R¹)_(n)) ringsimparting stereorigidity to said metallocene, Me, and imparting a chiralenvironment to a metal, Me, and R² is selected from the group consistingof an alkylene radical having 1-4 carbon atoms, a silicon hydrocarbylradical, a germanium hydrocarbyl radical, a phosphorus hydrocarbylradical, a nitrogen hydrocarbyl radical, a boron hydrocarbyl radical,and an aluminum hydrocarbyl radical; said Me is a group 4, 5, or 6 metalas designated in the Periodic Table of Elements; each Q may beindependently selected from a hydrocarbyl radical having 1-20 carbonatoms or is a halogen; and 0≦p≦3.
 11. The MCS as recited in claim 8wherein said metallocene is selected from the group consisting of: racdimethylsilanediyl bis(2-methyl-4-phenyl indenyl) zirconium dichloride;rac dimethylsilanediyl bis(2-methyl indenyl) zirconium dichloride, racdimethylsilanediyl bis(2-methyl-4,5-benzoindenyl) zirconium dichloride;and rac dimethylsilanediyl bis (2-methyl-4-(1-naphthyl) indenyl)zirconium dichloride.
 12. The MCS as recited in claim 8 wherein said MCScatalyzes the polymerization of a propylene comprising polymer gradepropylene further purified to having COS levels of less than about 20ppb, O₂ levels of less than about 5 ppm and H₂O levels of less thanabout 5 ppm.
 13. A process for the preparation of a metallocene catalystsystem (MCS) comprising: providing a support having a surface definingpores; and attaching a metallocene substantially throughout said supportto form a MCS having a catalytic activity for a metallocene loading ofabout 2 wt % that is at least about 20 percent higher than saidcatalytic activity for said metallocene loading of about 1 wt %.
 14. Theprocess as recited in claim 13 further including said support comprisingsilica, attaching an activator to said silica support substantiallythroughout said pore volume and attaching said metallocene to saidactivator to form said MCS.
 15. The process as recited in claim 13wherein said support is substantially spheroidal and said pores have apeak pore volume of greater than about 0.115 mL/g at a pore diameterbetween about 250 Angstroms and about 350 Angstroms.
 16. The process asrecited in claim 13 wherein said support is substantially spheroidal andsaid pores provide a peak surface area of at least about 14.3 m²/g at apore diameter between about 250 Angstroms and about 330 Angstroms.
 17. Aprocess for the polymerization of polyolefin comprising: preparing ametallocene catalyst system (MCS) having a catalytic activity for ametallocene loading of about 2 wt % that is at least about 20 percenthigher than said catalytic activity for said metallocene loading ofabout 1 wt %; introducing said MCS into a polymerization reactionchamber; and contacting at least one olefin monomer with said MCS insaid reaction chamber.
 18. The process as recited in claim 17 whereinsaid olefin monomer comprises an alpha olefin comprising ethylenicallyunsaturated hydrocarbons having between 2 and 20 Carbon atoms.
 19. Theprocess as recited in claim 17 wherein said olefin monomer is selectedfrom the group consisting of: a mixture of propylene and ethylene; amixture of propylene, butene and ethylene; and a mixture of propyleneand butene.
 20. The process as recited in claim 17 wherein said olefinmonomer comprises polymer grade propylene further purified to having COSlevels of less than about 20 ppb, O₂ levels of less than about 5 ppm andH₂O levels of less than about 5 ppm.
 21. A polyolefin produced by theprocess comprising: introducing a metallocene catalyst system (MCS) intoa polymerization reaction chamber said MCS having a catalytic activityfor a metallocene loading of about 2 wt % that is at least about 20percent higher than said catalytic activity for said metallocene loadingof about 1 wt %; and contacting at least one olefin monomer with saidMCS in said reaction chamber.
 22. The polyolefin as recited in claim 21wherein said polyolefin has an average particle diameter between about400 and about 2000 microns.
 23. The polyolefin as recited in claim 21wherein said polyolefin has an average particle diameter between about600 and about 1500 microns.
 24. The polyolefin as recited in claim 21wherein said polyolefin has a bulk density of at least about 0.37 g/cc.25. The polyolefin as recited in claim 21 wherein said polyolefin isconverted into a resin used for the manufacture of films, fibers orinjection molded articles.
 26. The process as recited in claim 21wherein said olefin monomer comprises polymer grade propylene furtherpurified to having COS levels of less than about 20 ppb, O₂ levels ofless than about 5 ppm and H₂O levels of less than about 5 ppm.